Masonry chimney vs insulated pipe

[kcbenson]

I'm finding I have to revise the way I think about chimneys. I've always believed masonry chimneys are inherently superior to insulated metal pipe chimneys, but every boiler vendor I've asked has said there is no advantage to a masonry chimney over insulated pipe. In fact, one vendor told me I would have to line the masonry chimney with stainless steel.

Since I already have insulated galvanized steel pipes available (old, but they're there), is there any reason I should be considering replacing them with a block chimney?

Ken Benson

 

[WRVERMONT]

No experience with "galvanized" insulated chimney but I have used the stainless variety many times. If your block chimney is to be located on the outside of the structure, definitely use the insulated metal chimney. A masonry chimney inside the house does have some benefits and less problems (more thermal mass, stays warm, etc.)

 

[kcbenson]

No, I was going to have a mason demolish and replace the three-flue insulated pipe chimney that's there now (inside, not outside the house) with a two-flue block chimney. Chimney chase (wood that surrounds the three flues up on the roof) is in rough shape, but would be pretty easy to fix. The pipes themselves probably need cleaning, but are otherwise probably okay. One of the three services the oil burner. The other two are not connected to anything.

In fact, the only reason I'm thinking about boilers now is because the mason needs to know what size flue for the boiler, and vendors are mostly telling me flue should be 6" round or as close as possible to that. Mason says smallest flue liner is 8x8" square. One vendor told me I was going to have to stick a 6" round pipe inside the 8x8" liner.

My thinking was that masonry will make a better draft, but vendors are telling me that's not so important with gasification boilers, which are "pushing" smoke up the chimney.

Does that sound right? Masonry chimney is going to cost $8,500. I can probably fix the existing chimney chase for a few hundred. Even if I have to replace galvanized with stainless, even if I have to replace two of them (one for the oil burner, one for the wood boiler), it's still going to be far less than $8,500, right?

Ken Benson

 

[heaterman]

IMHO, a stainless steel class A rated chimney is far superior in regards to performance under worst case scenarios (IE: chimney fire) I believe the rating standard for Class A is 2100* for a given number of minutes and 1,600* for a longer period of time. This of course is provided it is installed and maintained to manufacturers spec. I've been on our local fire dept for 30 years and have yet to see a Class A chimney fail under burn out conditions. I surely can not say the same for clay lined masonry chimneys.

 

[RobC]

I think you can only use galvy pipe for gas. Like greenhouse heaters.
When it gets used as a connector pipe from oil burner to chimney it's exposed, single wall and gets inspected when burner gets cleaned. Replaced when necessary.
Creosote is corrosive and galvy pipe is probably not to good for long term use with wood any way.
With all due respect to "heaterman" there has been a evolution in building codes with regards to masonry chimneys. Personally I would want a WELL BUILT masonry chimney if it was running through interior space.
Rob

 

[WRVERMONT]

Agreed, A stainless insulated chimney is safe, alternatively a masonry chimney with a stainless liner. There is nothing like a Well Built masonry chimney within the structure in my opinion. Ken, In any case I would reccomend installing a 8" round or equivalent flue for the Wood Boiler's flue. Good draft provided by an 8" flue can be balanced with a barometric damper.

 

[heaterman]

I think you can only use galvy pipe for gas. Like greenhouse heaters.
When it gets used as a connector pipe from oil burner to chimney it's exposed, single wall and gets inspected when burner gets cleaned. Replaced when necessary.
Creosote is corrosive and galvy pipe is probably not to good for long term use with wood any way.
With all due respect to "heaterman" there has been a evolution in building codes with regards to masonry chimneys. Personally I would want a WELL BUILT masonry chimney if it was running through interior space.
Rob

Agreed on the "well built INTERIOR masonry chimney". I can remember only one failure on an interior chimney and that one was very old. I can't say the same of an exterior chimney unless sound measures are taken to insulate it. With an exterior masonry flue it is very difficult to prevent flue gas condensation which of course leads to creosote formation and eventually a chimney fire.

 

[kcbenson]

No question interior is superior to exterior. And since the existing chimney is interior, it will stay that way. I grew up with an exterior chimney that developed a 15 ft crack over 3 years of use. My father took apart the house and rebuilt the brick chimney that served the oil burner with an extra flue for the wood stove. No problems after that.

The question is, does it make any sense to replace 6" or 8" (I'm thinking now there's both) round insulated galvanized pipe with a block chimney? At least one gasification vendor says I have to put 6" pipe inside the block chimney to make it work (is this the same as a stainless liner?), and all of them say that a metal pipe is just as good as masonry. One specifically says galvanized is okay, but won't last as long as stainless. I would be inclined to use the existing galvanized (after having a chimney sweep check it out) for a few years and then replace it with stainless.

If there's no reason to build a block chimney for a gasification boiler, then I could use the money for heat storage instead.

BTW, the oil-fired boiler is getting .4 percent efficiency over its rating using one of these 30-year-old insulated galvanized pipes.

What kind of chimney are you guys using?

Ken Benson

 

[heaterman]

No way would I advise galvanized for a wood flue, Olympic chimney supply makes really nice single wall stainless liners from either 304 or 316L material. I'd probably say go with an 8" flue as you never know what you might be sticking in there down the road. Draft regulation can easily be accomplished with a barometric damper.
I do question the need for a stainless liner if you are building a new masonry chimney with a liner in the first place. Try to get your hands on a copy of the NFPA codes for chimneys and vents to see what is called for by that organization.

 

[Piker]

My Family, prior to the passing of my father, was in the Masonry Construction business for decades. I will echo what others have stated; that a masonry fireplace can offer a lifetime of dependable use. Indeed, a chimney run up the inside of the structure will stay warmer and be less likely to produce condensate and creosote, although an exterior chimney if done properly can provide good results as well. Most of the exterior stainless pipe (double or triple wall) will probably last 20+ years or so... there are chimneys still in use today that my grandfather built in the early 1900's... and masonry construction materials have improved since then. It's all in the design.

That having been said, a good insulated stainless liner works pretty darn good too. Our fireplace uses a tarra-cotta liner, but the flue that runs to our basement is an 8x12 flexible stainless liner with insulation. Both have excellent draft.

I have long thought of picking up the tools of the masonry trade again... It's an enjoyable profession... and keeps you strong. I'll post a picture below of the chimney and fireplace that I built when we remodeled our house. It's 17' from the floor to the ceiling, and the stone was all hand cut from what I could find on the property. Took me several months of "spare time" to complete this structure. If you've seen the the Froling installation thread, you will see the angled foundation behind the boiler upon which all the stone work sits.


Cheers

 

[heaterman]

My Family, prior to the passing of my father, was in the Masonry Construction business for decades. I will echo what others have stated; that a masonry fireplace can offer a lifetime of dependable use. Indeed, a chimney run up the inside of the structure will stay warmer and be less likely to produce condensate and creosote, although an exterior chimney if done properly can provide good results as well. Most of the exterior stainless pipe (double or triple wall) will probably last 20+ years or so... there are chimneys still in use today that my grandfather built in the early 1900's... and masonry construction materials have improved since then. It's all in the design.

That having been said, a good insulated stainless liner works pretty darn good too. Our fireplace uses a tarra-cotta liner, but the flue that runs to our basement is an 8x12 flexible stainless liner with insulation. Both have excellent draft.

I have long thought of picking up the tools of the masonry trade again... It's an enjoyable profession... and keeps you strong. I'll post a picture below of the chimney and fireplace that I built when we remodeled our house. It's 17' from the floor to the ceiling, and the stone was all hand cut from what I could find on the property. Took me several months of "spare time" to complete this structure. If you've seen the the Froling installation thread, you will see the angled foundation behind the boiler upon which all the stone work sits.


Cheers

Now THAT is some nice work. I bet it makes a dandy radiator after it's had a fire in it for a day also. Very nice Piker. Very nice. True craftsmanship is easy to spot.

 

[benjamin]

When you say galvanized, is this refering to the outside layer of pipe, or the inside? There is triple walled uninsulated pipe that was commonly used for wood fireplaces, not sure how it's rated, but I've seen a lot of it, the inside is stainless, with two layers of galvanized steel. If I had 6 or 8" pipe of this sort, I would personally use it because that is a smooth wall pipe that should draft much better than the thin corrugated flexible liners I've seen. If it's two layers not insulated, or galv inside I wouldn't do it, it probably was never approved for that use.

The amish around here are all using a new system that looks like a porous insulating concrete round tile, 8 or maybe even 10 inches inside diameter over an inch thick walls, this gets installed inside standard chimney block and insulated with a granular loose fill insulation. I think that runs about $30 foot, without the block. They swear by it, well they don't swear but you know what I mean. I'm a little supicious of what creosote (acid) will do to concrete, the acid in sileage eats out a concrete silo eventually and this doesn't seem to have any way to avoid that. At least a clay liner is resistant to moisture and acid, even if the mortar around it turns to powder.

I checked into round clay tile at the local brick, block concrete supply place, they had 7" round for like $20 foot and 8x8" for a fraction of that, I ended up reusing some 90 year old clay tile liners, but I'd recommend the standard and cheap 8x8" if you want the mass etc, or whatever prefab class a is recomended if it's just going to be buried in a wall.

 

[Piker]

one of the nice things about the stainless liners is that the sections overlap so that if creosote or condensate is produced it will not be as likely to run outside of the liner. With the plain square ended tarra-cotta liners, it's pretty easy for creosote to run past the liners and into the cavity between the liner and the masonry (ie block/brick)... Which is generally not good. Best to have insulated over non-insulated regardless of liner materia to help keep the chimney clean.

cheers

 

[humpin iron]

Masonary vs stainless............one thought, 8x8 flue vs round...........when was the last time you saw a hawk doing "squares" in the sky.......spend your $$ on a new stainless chimney and rebuild the chase.

 

[kcbenson]

Just a followup:

I had a chimney sweep here last week who told me my pipes were triple wall "air insulated". The innermost pipe is stainless, surrounded by a layer of air, then galvanized pipe, then another layer of air, and an outside layer of galvanized. He said this is probably not adequate for a wood boiler, that the air layers (which are vented, so that they can pull in cold air) are going to chill the pipe and cause some creosote formation.

He also said that for this application a Class A stainless chimney is going to work just as well as a lined masonry chimney, better than an unlined masonry chimney, which is what I had planned on. Replacing an existing chimney with Class A pipe and rebuilding the rotting chimney chase should cost about $1000 (doing it myself).

The chimney sweep has a 4-year-old 100,000 BTU Tarm with 600 gallons of storage at home, and he offered to let me visit next time he fires it.

Ken Benson

 

[RowCropRenegade]

Beautiful mason work, Piker.

Simply, awesome.